This invention relates to the surgical biopsy excision of tissues, particularly but not exclusively the excision of abnormal lining in the uterine cervix.
Cancer of the uterine cervix, or cervical cancer, usually progresses slowly over an extended period from the first appearance of pre-cancerous abnormalities. With today""s sophisticated screening programs involving regular smear testing, colposcopy and so on, this gradual progression presents an opportunity for many patients entirely to avoid cervical cancer if they can benefit from preventative intervention. Even for those who do not, there is a good prognosis if the cancer is detected and treated early enough.
Before malignant cells are found, the tissues of the cervix go through changes in which abnormal cells begin to appear, initially on the epithelial tissue on the surface of the cervix. This precancerous condition is known as dysplasia or cervical intraepithelial neoplasia (CIN).
CIN does not directly infer cancer but refers to a spectrum of abnormality ranging from mild dysplasia, that may regress without intervention, to severe dysplasia that may extend to carcinoma-in-situ, the cancer initially being localised to the intraepithelial tissue or superficial layer of the cervix. If left untreated, the cancer cells will start to grow and spread more deeply into the cervix and to surrounding areas, necessitating hysterectomy at best and, of course, threatening the patient""s life.
If left untreated, around 30% to 50% of CIN conditions may progress to invasive cancer. Clearly, detection and treatment of CIN is essential to avoid the possible development of cervical cancer.
CIN is a lesion of abnormal cells typically associated with the Human Papilloma Virus (HPV). When HPV is contracted, it infects the cells of the transformation zone of the cervix where the cells of the cervix actively divide and grow. As those cells grow and mature, they are pushed to the surface as new cells are produced and the older, outside cells die and are shed. When the virus infects the cells and then becomes active, abnormal cells begin to be produced in the transformation zone and a lesion develops in the epithelial tissue at the surface of the cervix.
Removal of the lesion is an effective treatment for CIN. Although HPV remains once the CIN lesion is removed, the rate of recurrence of CIN is quite low since the removal of the transformation zone eliminates the tissue most susceptible to CIN.
Lesioned or dysplastic cells may be removed by cauterisation, cryosurgery or laser surgery. Cauterisation uses heat, electricity or chemicals to burn the abnormal tissue off the cervix. Cryosurgery freezes the cells and laser surgery destroys the cells with a laser beam. Various specific techniques include cryocautery, cold coagulation, large loop excision of the transformation zone, diathermy, needle excision of the transformation zone, cold knife cone biopsy, laser ablation, laser cone and a combination of cutting diathermy cones.
A common cervical excision procedure employs loop electrosurgery, sometimes called the Loop Electrosurgical Excision Procedure or LEEP. LEEP uses a thin wire loop electrode connected to an electrosurgical generator that emits an electric current to cut away affected tissue. A low voltage and relatively high frequency electric current is emitted from the loop into the tissue cells in the immediate area of the loop wire. Consequently, the cells heat rapidly, generating steam that causes the cells to burst microscopically and thus divides the tissue as the wire moves through the tissue. The wire is typically swept across the projecting neck of the cervix, or ectocervix, thereby removing a thin annular slice of tissue.
Unlike most other treatment methods, particularly ablative methods such as laser surgery, LEEP allows the physician to have the excised specimen analysed by a pathology laboratory. This allows for more accurate assessment of the abnormal tissue, which will confirm either that the lesion has been completely removed with the biopsy sample or, if it has not, what further treatment may be necessary.
The entire LEEP procedure usually takes less than fifteen minutes and is generally very effective and well received by patients. However, LEEP has its complications.
Because LEEP utilises electric current, burns to the vagina and other surrounding tissue may occur; such injury will cause unnecessary discomfort during and after the procedure, and may substantially lengthen the patient""s recovery period.
Another problem of inaccurate use of a loop electrode is that the sample of tissue obtained may vary in amount and definition. LEEP is particularly prone to producing fragmented and burnt biopsy samples if it is necessary to make multiple passes of the loop, which reduces the accuracy of diagnosis. Multiple passes are particularly needed where, as is common, a lesion extends into the endocervical canal.
Incomplete removal of the lesion when excising the transformation zone is another, much larger potential risk, since this can only worsen the patient""s long-term prognosis and will require further procedures to remove the remaining abnormal cells. This puts the patient through further unpleasant and emotionally draining treatment. The converse risk is the removal of too much tissue, which may result in cervical stenosis, an incompetent cervix, and/or sterility.
The underlying problem of LEEP is that the loop electrode is generally on the distal end of a long handle for which there is no guiding support in use. Once energised, the loop will instantly cut into and burn any tissue with which it comes into contact and so accurate positioning is critical both upon encountering the cervix and during excision of cervical tissue. Not only must the head of the instrument be placed exactly where it is needed before excision starts, but also the movement of the wire must be carefully controlled during its excising pass across the cervix. The lack of support makes it difficult for even an experienced physician to achieve an accurate cut; the problem is worse if the operating physician is inexperienced, particularly where visibility of the lesion is poor.
The inherent lack of stability of the loop electrode is exacerbated because the electrode itself can move in relation to the handle under the influence of drag as the electrode passes through the cervical tissue. This compounds the difficulty of knowing exactly where the electrode is at all times, and thus adds to the difficulty of producing an accurate cut.
Owing to the problems outlined above, there have been attempts to modify the standard loop cervical biopsy device. The most notable modification is described in International Patent Application No. PCT/US95/01262 to Fischer, published as WO95/20922.
The Fischer instrument described in WO95/20922 has an elongated insulated body member with an endocervical portion at the distal end, a contact portion at the proximal end and a vaginal portion in between. An insulated stop arm extends at right angles to the body member from the junction of the endocervical and vaginal portions. A wire electrode extends diagonally between the stop arm and the endocervical portion.
The Fischer instrument is sold by a US company, Apple Medical Corporation. It has come to be known among physicians as the Fischer cone biopsy device or simply as the Fischer cone, which term will be used hereafter for brevity.
In use, the Fischer cone is connected by means of the contact portion to an electrosurgical generator such as a blend cutting diathermy machine. The instrument is then inserted into the cervix through the vaginal canal, the vaginal canal being held open by a duckbill speculum as is well known in the art. The endocervical portion is aimed into the cervical canal to gain support for the distal end of the instrument, whereupon the wire is energised through the contact portion and conductor means within the insulated body.
When the energised wire contacts the cervical tissue at the ectocervix, a current passes through the wire into the patient to return through an electrode attached to a convenient part of the patient""s body. This current heats the tissue cells adjacent the wire until they burst. The wire is then advanced through the cervix, separating the cervical tissue, with the endocervical portion extending further into the cervical canal until the stop arm touches the ectocervix. When this position is reached, the instrument is turned one full revolution (360xc2x0) about its longitudinal axis to cut a conical tissue specimen from the transformation zone. The current is then turned off and the cut specimen is withdrawn with the instrument from the vaginal canal.
The endocervical portion extending into the cervical canal acts as a pivot about which the Fischer cone is turned during the cutting operation, the pivot rotatably supporting the distal end of the instrument. Also, the arm abutting the ectocervix acts to determine the depth of cut during the cutting operation. Optionally, a bi-directional arm seats the instrument on opposite sides of the cervical canal to increase stability during rotation. To an extent, therefore, the Fischer cone allows the excision to be performed partially by feel.
The accuracy of the Fischer cone is improved further over the loop electrode because the arm holds the diagonal electrode taut and straight throughout the procedure, and because the electrode itself is as short as possible.
Whilst the improved stability, ease of use and hence accuracy afforded by the Fischer cone have been well received among physicians, the Fischer cone also has its drawbacks.
One problem is that every abnormal cervix is unique in its size and shape and in the position, depth and extent of the lesion. The only way of adapting the Fischer cone to these variations is to provide a preordained range of instruments that differ in the length and angle of the diagonal electrode. This leaves the physician to select an appropriate one of the range, hoping that the patient and the necessary biopsy sample accord with one of the available instruments.
Of course, it rarely happens that the chosen instrument exactly suits the cervix and lesion in question. Lesions are rarely evenly distributed around the transformation zone and, indeed, may be deeper in some areas compared to others. Consequently, when using the Fischer cone, if more tissue must be removed from one area of the cervix compared to another, the less affected area will be subjected to unnecessary damage that may ultimately cause the same problems encountered with LEEP. The only way around this is to make a partial cut by turning the instrument through less than 360xc2x0, or locally to reduce the depth of cut by partially withdrawing the instrument during the cutting sweep. Neither technique uses the Fischer cone to its best advantage.
A further drawback of the Fischer cone is the need to turn the instrument through a full 360xc2x0 when it is desired to make a full conical excision. This introduces the possibility of error because the physician must change his or her grip on the instrument during the excision movement: the physician""s wrist cannot turn through 360xc2x0. The possibility of error is heightened if the cervical canal is wider than the endocervical portion of the instrument, as is common in so-called patulous or stretched-open cervices: the cervical canal cannot then receive the endocervical portion snugly enough to create a fixed pivot point and hence cannot center the endocervical portion accurately.
The range of just five Fischer cone configurations currently on sale cannot possibly cater for all situations. The result of this is that use of the Fischer cone may still require the physician to apply considerable skill by controlling the movement of the instrument in a particular way during excision.
Whilst skill will always be required successfully to perform a cervical biopsy procedure, there is a need to improve the accuracy, efficacy and ease of use of existing instruments. The present invention has arisen from this background and has been developed with that need in mind.
From one aspect, the invention resides in a cervical biopsy instrument comprising:
a shaft defining a longitudinal axis and having a proximal end and a distal end;
an arm extending laterally from the shaft;
a cutting wire capable of cutting tissue when current is supplied to the wire in use through conductor means in the shaft, a cutting portion of the cutting wire being supported at an outer end by the arm and being inclined relative to the longitudinal axis such that the cutting portion of the wire converges with the longitudinal axis moving from the arm towards the distal end; and
means for adjusting and setting the inclination and/or length of the cutting portion.
The facility for adjusting and setting the inclination and/or length of the cutting portion confers adaptability on the instrument of this invention. It enables a single instrument to deal with differently-sized, shaped and positioned cervical lesions in a manner that is clinically effective but minimally invasive. Put another way, the invention helps a physician to strike the difficult balance between excising too little, potentially endangering the patient""s life through failure to halt the onset or progress of cervical cancer, and excising too much, potentially leading to an incompetent cervix and the end of the patient""s reproductive capacity.
It is preferred that the inclination and/or length of the cutting portion are steplessly adjustable to allow the instrument to be tailored precisely as the physician may require.
Whilst it is preferred that the cutting portion extends from the outer end supported by the arm to an inner end supported by the shaft at or near the distal end, the inner end of the cutting portion need not be supported directly by the shaft but could be supported by some other support structure that is supported in turn by the shaft.
In particularly preferred embodiments, a plurality of arms extend laterally from and are angularly spaced about the shaft, each arm supporting a respective cutting portion at an inclination relative to said longitudinal axis such that the cutting portions converge with the longitudinal axis approaching the distal end. More preferably, at least first and second arms are opposed about the shaft so that the cutting portions of cutting wire supported by those arms are substantially coplanar.
By providing more than one arm on the instrument of the invention and by disposing those arms around the shaft in, for example, a diametrically-opposed, 180xc2x0-spaced arrangement, the physician need not turn the instrument through a full 360xc2x0 in order to excise a full conical tissue specimen. Instead, a 180xc2x0 turn will suffice and an even smaller turn will suffice if more than two arms are used. In general, the less angular movement the physician needs to effect, the better the chance of a consistent and correct position and depth of cut. Nevertheless, two arms are deemed sufficient for the purposes of the invention and are preferred to a greater number of arms.
Of course, a physician need not necessarily cut through a full 360xc2x0: preferred embodiments of the invention provide for adjustment of the instrument to avoid cutting, or to reduce the depth of cut, on one side of the cervix. For example, it is contemplated that the or each arm can be variable in length and, if there are two or more variable-length arms, that the length of one arm can be adjusted independently of the or each other arm. Also, it is always up to the physician how far he or she wishes to turn the instrument and therefore how much he or she wishes to cut.
The provision of more than one arm also aids centering of the instrument within the cervical opening both upon insertion of the instrument and during excision of tissue. The relative symmetry of the instrument, and the closer equality of drag forces experienced on both sides of the longitudinal axis during turning, lends a degree of self-centering that is absent in the asymmetric prior art instruments.
It is further preferred that the or each arm is movable during adjustment in a direction parallel to the longitudinal axis with respect to the distal end of the shaft. To that end, the or each arm may be mounted on a carriage mounted in turn to the shaft for movement along the shaft. For simplicity, this longitudinal movement of the or each arm is preferably a sliding movement that keeps the arms in fixed angular relation to the shaft.
Where the position of the inner end of the cutting portion is fixed with respect to the distal end of the shaft, moving the or each arm in this way without changing its length will tend to lengthen or shorten the cutting portion and to alter its angle of inclination with respect to the longitudinal axis. This is one way of adjusting the instrument to excise an appropriate part of the cervix.
To aid correct positioning, the shaft may have graduation means visible during adjustment to indicate the position of the or each arm with respect to the distal end of the shaft. To keep the correct position, means are suitably provided for locking the carriage to prevent movement of the carriage with respect to the shaft.
In another way of adjusting the instrument to excise an appropriate part of the cervix and as mentioned above, the or each arm is variable in length with respect to the longitudinal axis to vary the distance of the outer end of the associated cutting portion from the longitudinal axis. Whilst many variously complex ways to achieve this will be apparent to those skilled in the art once given the inventive concept, it is preferred in this invention simply that the or each arm is plastically deformable to the extent that it can be bent before use to adjust its shape and length and will then hold that shape and length in normal use of the instrument.
Where there are two or more variable-length arms and the length of one arm can be adjusted independently of the or each other arm, an asymmetric cut can be achieved by a simple turn of 180xc2x0 or less. This can be of singular importance where, as is common, the lesion is asymmetric or the cervix is distorted and so it is desirable not to excise tissue to the same depth around the entire cervix.
Again, altering the length of the or each arm in this way without changing its longitudinal position with respect to the distal end will tend to lengthen or shorten the cutting portion and to alter its angle of inclination with respect to the longitudinal axis.
In practice, the different forms of adjustment provided by preferred embodiments of the invention can be used together with great flexibility. In this way, a physician can tailor the instrument to deal with the particular cervix and lesion concerned, without having to use one of a range of different instrumentsxe2x80x94none of which may be quite right for the task in question.
If the cutting portion is shortened by either of the above means of adjustment, retractor means are advantageously provided to retract excess cutting wire and thereby to keep the cutting portion taut and straight. The retracted cutting wire can be held in storage means, to be paid out if the cutting portion is lengthened. For compactness and robustness, the retractor means and the storage means are preferably within the shaft although it is conceivable that these means could be exposed. It is further preferred that the cutting portion is fixed at its outer end to the arm and that its inner end is supported by the shaft in a manner that allows the cutting wire to move under the influence of the retractor means as the cutting portion is varied in length. This simplifies the construction of the or each arm. It would, however, be possible to reverse the arrangement such that the cutting portion is fixed at its inner end to the shaft and is supported at its outer end by the or each arm in a manner that allows the cutting wire to move as the cutting portion is varied in length.
In any arrangement, it is highly advantageous that the retractor means maintains tension on the cutting portions after adjustment. Conveniently, the retractor means comprises spring means acting in tension. There may be first and second spring means, the first spring means being disposed distally with respect to the second spring means and the spring means being offset longitudinally from each other to an extent necessary to permit their maximum extension in use. In that event, there is room for both spring means even when they are within a tubular shaft portion and have an aggregate diameter greater than the internal diameter of that shaft portion.
In an alternative arrangement, the first and second spring means are at longitudinally corresponding positions beside each other. In that event, the first and second spring means are preferably segregated from each other to ensure that each can operate without interference from the other. An elegant development employs common spring means acting on both of the first and second wires to tension and retract the cutting portions. The partition between first and second wires suitably has an opening through which the common spring means extends.
As the opening of a stretched or patulous cervical canal may be wider than the shaft, a centering means is preferably provided that is movable along the shaft in a direction parallel to the longitudinal axis, the centering means being advanced towards the distal end of the shaft to engage, in use, within the cervical canal. To cater for different sizes of cervical canal, the centering means preferably defines a cervix-engaging surface that tapers towards the distal end of the shaft. In a simple arrangement that achieves this objective, the centering means is a frusto-conical collar around the shaft that can be advanced along the shaft when it is desired effectively to widen the shaft to fit a patulous cervix.
This aspect of the invention has independent applicability and therefore the invention may also be expressed as a cervical biopsy instrument comprising a shaft defining a longitudinal axis and having a proximal end and a distal end, a distal end portion being received in use within a cervical canal to form a pivot for an angular excision movement about the longitudinal axis, the instrument further including centering means positionable at the distal end portion to center the shaft within a cervical canal that is wider than a transverse diameter of the distal end portion.
To avoid interference with the insertion of the distal end portion into a normal cervix, the centering means preferably has a parked position disposed proximally with respect to the or each arm. The centering means can then be advanced into a cervix-engaging position disposed distally with respect to the or each arm.
Where the centering means is a collar around the shaft, the collar can resiliently grip the shaft or the centering means and the shaft can have complementary threads by which the centering means can be moved longitudinally with respect to the shaft.
From another aspect, the invention in its broadest sense does not require adjustability of the angle and length of the cutting portion but instead resides in a cervical biopsy instrument comprising:
a shaft defining a longitudinal axis and having a proximal end and a distal end;
a plurality of arms extending laterally from and being angularly spaced about the shaft, each arm supporting a respective cutting portion of cutting wire being capable of cutting tissue when current is supplied to the wire in use through conductor means in the shaft;
each cutting portion being held by a respective arm at an inclination relative to said longitudinal axis, said inclination being such that the cutting portions converge with the longitudinal axis approaching the distal end.
As before, it is preferred that first and second arms are diametrically opposed about the shaft so that the cutting portions of cutting wire supported by those arms are substantially coplanar.